Figure 3.

Ixazomib suppresses blood 20S proteasome activity. Whole‐blood samples acquired at baseline and on cycle 1 day 11 at 2 hours postdosing were analyzed by β5 chymotrypsin‐like proteasome activity assay. Although proteasome activity was widely variable at baseline, postixazomib samples showed a significant decrease of proteasome activity compared with baseline (Fig. 2; two‐way analysis of variance [ANOVA] time effect p = .026). The postixazomib samples showed residual proteasome activity, which was not significantly different between dose cohorts, suggesting that maximal proteasome inhibition in blood was achieved with the lowest dose (2.3 mg) of ixazomib in this study. Luminescence per sample is shown according to dose cohort. Data were analyzed by two‐way ANOVA followed by Tukey‐adjusted comparisons between dose cohorts, which revealed only a statistically significant effect of time on proteasome activity. Abbreviation: RLU, relative luminescence unit.